Field of Endeavor
The present invention relates to batteries and more particularly to a battery management systems with thermally integrated fire suppression.
State of Technology
The most critical issue facing widespread adoption of rechargeable lithium ion batteries in large scale, vehicular applications is safety. Once these batteries reach internal temperatures of approximately 90° C., self-sustaining exothermic reactions trigger dangerous thermal runaway. The cause of these events can be internal or external short from a variety of causes, included crushing, containment penetration, external heating events, or manufacturing defects. In addition, these batteries are also significantly overdesigned to compensate capacity loss through cycling at moderately high temperatures, with significant capacity loss occurring above ˜50° C. for virtually every commercially applicable cell chemistry. Furthermore, these batteries contain a low thermal conductivity plastic (e.g., polyethylene or polypropylene) separator soaked in a non-aqueous electrolytic solution. As a result, when multiple cells are stacked together, it is difficult to remove heat from the more thermally insulated portions of the battery. This makes mitigation of thermal runaway even more difficult, and can cause localized cycling of the battery, which can lead to premature aging.
International Patent Application No. WO 2010/025761 for a system for fire protection provides the state of technology information quoted below. International Patent Application No. WO 2010/025761 is incorporated herein by this reference.
“Power transmission networks sometimes utilize backup power systems, for example in order to compensate for varying power generation or load, or in the case of loss of power. This can for example be the case in wind- or solar power systems. The backup power system provides power during fluctuations of the generated wind or solar power and even during power outages.”
“Such backup power systems rely on a bank of batteries to store enough energy to even out the power fluctuations. In power transmission networks such battery storage systems may consist of a large amount of battery cells connected in series and parallel to reach sufficiently high voltage levels and high power and energy. The voltage levels may be in the order of several tens of kV and power capability up to several 10 MWs or even in the order of 100 MW. To achieve this, such battery energy storage systems will comprise several thousands battery cells.”
“The batteries of the backup power thus contain high amount of energy, and a failing battery cell, e.g. by external or internal short circuit or overload, will quickly become very hot. The heat emitted from the failing cell will heat up an adjacent battery cell, which in turn will heat up the next cell and so on, and this of course constitutes a huge fire hazard. As an example, Li-ion battery cells exceeding a critical temperature may result in opening of the cell, known as venting of the cell, with a release of highly inflammable gases that can easily catch fire. If this happens there is a large risk of the whole battery storage system being destroyed.”
“The gases released from Li-ion battery cells may contain a mixture of hydrogen, carbon monoxide, carbon dioxide, methane, ethane, methylene, propylene, organic carbonates and also carbon powder. The battery backup systems are therefore usually protected by temperature sensors detecting heat of a fire and by fire extinguishing means, for example argonite based fire extinguishers. Argonite gas is injected rapidly into the storage room within which the battery backup is stored, when the temperature sensors detect an abnormal temperature.”